I believe its a mint mark, kind of like PDS for us (and W). What I seem to recall is that some coins are minted abroad and others in Canada. The Royal Mint uses a P, I believe. It's been a while now, so don't quote me.
I thought I did. I filled most of the Whitman folder I had before trading with the fellow up north. Then I learned of many more varieties/mint marks/magnetic coins, etc. That's when I decided to buy the Canadian Albums for Cents and Nickels. I filled those as full as I could out of my Whitmans...then trading time began. I had to purchase the Large Cents, since these aren't in circulation. But I would come across one, here or there, mainly at antique stores here on the shore of CT. I'd get them for a quarter or so. Most didn't even know what they had.
The Canadian Cents have a mint mark on some coins and designers initials are also on them. The capital P stands for which ones are Plated. No P, they are not plated.
I pull that scam when I was young! It was with dimes though. They didn't catch me but one day there was a handmade sign at the cashier stating "No Canadian Coins"! BTW one day I did get an Indian cent in my change from the lunch lady.
I never knew that! I wish the US Mint had done something similar for Zincolns. Then we'd have a whole new class of mint errors, where a non-plated planchet got the P, or a plated one didn't get it. Or better yet, instead of a P (which would get confused with the Philadelphia mint mark), we could have a privy mark. I propose something like this: